After your swallowtail caterpillar has formed a chrysalis in a lunch sack, "gizmo", or other suitable area, attach your pupa to a container laced with paper towel; so that it has sufficient room to emerge and pump out its wings.  When a butterfly first emerges, its wings are as soft as butter.  (No pun intended).  It usually takes a few hours for its wings to harden up before its ready to fly.  If you do turn your butterfly loose, be sure to release it in the same habitat and location as where you found it.